1. Field of the Invention
The present invention relates to a current sensor, specifically to a sensor which will detect an AC current, or a fast variation of a DC current, and will produce a signal proportional to this variation.
2. Description of the Prior Art
The methods and devices used for current detection by prior art, are based on the Rogowski Pickup Coil, presented in FIG. 1. This sensor comprises a coil 27, inserted between two conductors 25 and 26, each carrying opposite sense currents 10 and 11, one of each is wrapped around the coil, so as to offer a better magnetic coupling with the coil. The variable magnetic field generated by the conductors, will generate a signal into the coupled coil. This layout implies a very difficult manufacturing process, with many parts involved, like the coil, a support for the coil, an insulator, a cylindrically formed conductor, and a case to hold them all together.
The main object of this invention is to provide a very versatile, easy to manufacture, extremely compact, low cost current sensor, especially for high currents, and which will not interfere in any way with the current flow, which will not draw power or dissipate almost none of the energy offered by the system. The present invention is an inductance, designed in a vertical and a horizontal layout, which is used to collect magnetic field lines from the field generated by the current carrying conductor, both the inductive sensor and the conductor being PCB copper traces, on a PCB board. Thus, the sensor will not practically be a discrete component to be mounted on the PCB, but will be manufactured as part of the interconnection layout of the electronic application (schematics) with little if any cost added to the total cost of the electronic PCB board. The sensor will produce a signal, which will be proportional to ramp of variation of the current in the main conductor. The sensor may be positioned in two places when dealing with single current conductors: the sensor may be located either on top/bottom of the planar conductor, crossing/collecting the field lines which pass across the conductor, or sideways, collecting the more close together field lines in this area. When dealing with two parallel conductors, carrying opposite sense currents, the sensor will be placed between the two conductors, with the traces parallel to these conductors, collecting the field lines of both conductors, which will be packed together in between the conductors. In most of the applications the current carrying conductor and the return current path plane are located in very close to each other to minimize the parasitic inductance. The magnetic field is concentrated in between these to planes. The sensor loop is located in between these planes wherein the magnetic field lines are concentrated. This is the layout offering the highest output signal. The number of loops and the number of necessary layers will depend upon the application, the available space and the current slope.